- You won’t get this quest until you get most of the way through Ladies of the Wood. It won’t end when you get The Whispering Hillock, but completing this quest is a prerequisite for finishing that quest.

- The Hillock’s located to the southeast of Downwarren. You may run into Drowners along the way, if you take a direct route there, but of more concern is a level fourteen Alghoul haunting the side of the road just south of Downwarren. It’s a frightful powerful creature if you come here before you hit your teens, and you’re better off avoiding it unless you’re over-levelled for the area.

- Upon hitting the large yellow circle of interest you’ll start hearing a voice that tells you to go back. If you search the eastern side of the Hillock you’ll quickly find a single Werewolf, protecting a Place of Power. Kill it and you can claim the Power for yourself. Werewolves are tough bastards, given their high regenerative capabilities, but you can mitigate the regen factor either by using potions to increase your damage output or simply cornering the Werewolf against the rocks and slashing at it until it dies. So long as the Werewolf can’t bound away you can get in a lot of hits.

- Near the Place of Power you’ll find the Entrance to a cave. Dip into the water straight ahead And swim around the obstruction in the cave, using your Witcher Senses underwater to pinpoint and loot three chests found below. You’ll soon hit a cut scene as you enter an open chamber.

- The spirit of the Hillock begs you to free it from its prison. You have three options on how to proceed:

Refuse to help the spirit. This will put you in a battle against several Endrega Workers and the Tree’s Heart. It’s a boss, but this fight is easy. Kill a few Endregas, then use Igni on the Heart. This will knock the vines protecting it out of the way for a few seconds. Slash until it covers itself again, then repeat with Igni. It will die really fast.

Agree to help the spirit. You’ll be tasked with finding three things: Raven Feathers, a horse, and the spirit’s mortal remains. More on this below. Note that even if you do this you can still choose to kill the spirit.

Agree to help the spirit before getting the quest by visiting the Ealdorman. This results in a happier ending for all involved, but is otherwise the same as agreeing normally. (Might also be a bit of a glitch, from what I've read, but there you go.)

The spirit of the Whispering Hillock.
May be more evil than it implies. Shocking!

Item Collecting

Agree to help the spirit and you’ll need to find three items. They’re all pretty easy to obtain:

The Raven Feathers were likely found during Ladies of the Wood. They’re located in the same nest where you found Johnny’s voice.

The remains are found to the northwest of the Hillock. They’re guarded by a Water Hag. Once you kill the Hag, check the south of the area of interest for a small, unremarkable tombstone.

Several black horses can be found to the south of the Hillock, at the Crossroads Fast Travel signpost. Use Axii on one of them to calm it, then climb aboard.

What happens past this point will depend on your choices, though in the long run it’s pretty much guaranteed that someone is going to die - and this is particularly true if you actually save the spirit of the tree.